6 December 2006
Including change 1, 7 December 2006
Table 7-4. Grounding of Substation Equipment
Grounds must be in place before a tank is opened and the insulating medium
(oil/gas) is changed. This does not apply to sampling when using a sampling
Switches may not be used to maintain personal ground continuity except when
the switch is specifically designed for that purpose.
Allow at least 5 minutes between opening of the capacitor switching devices
and the closing of the ground switch on a fully charged capacitor bank. wait at
least 5 minutes after the ground switch is closed before installing protective
grounds. Maintain a capacitor bank deenergized for at least 5 minutes before
re-energizing it. Include the time limits required for these maneuvers in
switching orders involving capacitor banks.
Disconnect and discharge surge arrestors using grounding cables.
Do not work on grounding transformers unless they are deenergized and
properly grounded. Isolate phase reactors from all energized sources and
ground them before starting work on them.
Disconnect bushing leads from bushing terminals as necessary to permit
equipment testing that requires the equipment to be ungrounded. Use a hot
stick to connect test equipment and re-establish the ground as soon as the test
is completed. Following an applied potential test ("Hi-Pot"), ensure the ground
remains in place for a period at least two times the duration of the test period.
Follow the manufacturer's recommendations for work clearances and
grounding instructions for the test equipment
Install separate grounds for each isolated section of the deenergized circuit if a
hazard exists when working in a deenergized area of a substation where there
are one or more physical breaks in the electrical circuit.
Table 7-5. Grounding of Equipment During Oil Handling
Bond apparatus tanks, conductive hoses, pumping or filtering equipment,
drums, tank cars, trucks, and portable storage tanks to the station ground mat.
Connect the vehicle end first and disconnect it last to prevent possible arcs
near the vehicle.
Bond exposed conductors, such as transformer or circuit breaker bushings, or
coil ends or transformers where bushings have been physically removed, to the
same grounding point.
AERIAL LIFT TRUCK VEHICLE GROUNDING. Ground and bond each
vehicle being used at the job site when any parts of it will come within the clearance
distances of Table 3-1. When in transit or when parked with no load and all booms
lowered, the vehicle may be ungrounded if it is located outside the minimum distances.